It is generally known to compound thermoplastic resins with fillers, such as glass, particles, fibers and other like materials. In addition, it is known to pelletize said filled thermoplastic resins to form filled pellets for storage and/or transport of said filled thermoplastic resins. Typically, a thermoplastic resin is heated to form a melt, whereby the filler, such as the glass, particles, fibers and other like materials are added to the melt to form a melted filled thermoplastic resin. The resin is then typically extruded to form articles, or extruded for pelletizing.
More specifically, it is further known to compound thermoplastic resins with fiber rovings for the production of long fiber-reinforced thermoplastic resins. When the fiber roving is a glass fiber roving, the typical fiber loadings in such compounds vary from about 30% to about 60% glass fiber by weight, although certain products exist in concentrate form with fiber loadings up to about 75% by weight glass fiber. However, such concentrates are typically characterized by excessive loose fiber, poor dispersion in molded articles, and generally poor pellet integrity.
For example, U.S. Pat. Nos. 4,312,917 and 4,439,387 to Hawley relate to compound composite structure that is a combination of plastic and other materials, including glass fiber, for forming a structure usable in the fabrication of manufactured products or components. The compound composite structure is composed of a thermoplastic resin material bonded to, by mixture with, a composite reinforcing structure. The composite reinforcing structure consists of fibers imbedded in a thermoplastic resin material, and may be formed by passing molten plastic resin material through a die which imbeds fibers.
In addition, U.S. Pat. No. 5,514,745 to Yoshino disclose a mixture for melt process moldings consisting essentially of about 5 to about 70 weight percent of a master batch prepared in the form of pellets formed by cutting a long glass fiber-reinforced polypropylene resin, and about 30% to about 95% by weight of polypropylene resin. The long glass fiber-reinforced polypropylene resin is prepared in such a manner that a bundle of continuous reinforcement glass fibers surface-finished with a finishing agent containing a coupling agent is impregnated with a modified polypropylene resin having a functional group capable of chemically bonding with the coupling agent and having a melt flow rate of about 70 to about 300 g/10 min (ASTM D-1238, load: 2.16 kg, temperature: 230° C.) while the bundle of glass fibers is being drawn. The pellets have a length of about 2 to about 50 mm in the direction along the fibers. The glass fibers in the pellets extend uniformly in parallel with each other through a distance substantially equal to the length of the pellets. The pellets have a glass fiber content of about 60 to about 90 weight percent.